ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Synthesis and characterization of a novel Schiff base and its enhancement on flame retardancy of epoxy resins

Ge-Yun You, Hong-Wu He, Bin Feng, Yu-Ying Tang, Fang-Fang Fan, Zhi-Quan Cheng, Chang-Jie Yang, and Cong Liang

College of Chemistry and Environmental Engineering, Baise University, Baise, People’s Republic of China

E-mail: yougeyun1988@163.com

Received: 25 July 2019  Accepted: 13 January 2020

Abstract:

A novel Schiff base, namely N¹,N²-bis{3,4-bis(5,5-dimethyl-2-oxide-1,3,2-dioxaphosphinan-2-yl)oxy]benzylidene}ethane-1,2-diamine (PN), was synthesized by the condensation of 3,4-bis[(5,5-dimethyl-2-oxido-1,3,2-dioxaphosphinan-2-yl)oxy] benzaldehyde (PCHO) and ethylenediamine. Its chemical structure was characterized by ¹H, ¹³C, ³¹P NMR, mass spectra and elemental analysis. PN was used as an additive flame retardant to improve the flame retardancy of diglycidyl ether of bisphenol A (DGEBA) cured by 4,4′-diaminodiphenylsulfone (DDS) with different phosphorus mass fraction. The incorporation of PN promoted DGEBA/DDS to yield more char residues under both nitrogen and air atmosphere, and exhibit good flame retardancy. With 1.5 wt% phosphorus mass fraction, PN-1.5/DGEBA/DDS could reach the highest flame retardant level of V-0 rating for UL-94 vertical burning test, obtain a limiting oxygen index (LOI) value of 32.4%, and keep relatively good mechanical properties by 81.52% of flexural strength and 90.40% of Izod impact strength compared with DGEBA/DDS. The flame-retardant mechanism researches revealed that PN presented a comprehensive mechanism of condensed phase, gas phase and phosphorus-nitrogen synergistic effect in DGEBA/DDS system.

Keywords: Epoxy resin; Phosphorus-nitrogen; Flame retardancy; Mechanical performance; Flame-retardant mechanism

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-020-01067-8

Chemical Papers 74 (7) 2201–2210 (2020)